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CAHSEE Math 5.1 Algebra I 208 Views
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Description:
Algebra I: Drill 5, Problem 1. A line parallel to another line whose graph passes through the point (3, 8) and has a y-intercept of -1 must have a slope of what?
Transcript
- 00:03
Here’s an unshmoopy question you may find on an exam somewhere in life…
- 00:07
A line parallel to another line whose graph passes through the point (3, 8) and has a y-intercept
- 00:13
of -1 must have a slope of… what?
- 00:17
And here are the potential answers…
- 00:22
So… what is this question asking?
Full Transcript
- 00:23
How well do we really know the point slope formula, y equals mx plus b?
- 00:29
First of all, this whole “line is parallel” business is just the test-makers trying to trip us up.
- 00:35
All parallel lines have the same slope, so let’s not fall prey to their wily schemes.
- 00:39
So in the y equals mx plus b format of describing a line, we have b already – it’s negative 1…
- 00:46
the problem tells us that much.
- 00:48
So we now just have to solve for slope by taking what we know and plugging it into the base equation.
- 00:53
Well, b is negative 1 so it’s:
- 00:56
y equals mx minus 1
- 00:58
But the problem GIVES us the point 3, 8, which we know the line passes through…
- 01:03
so we can simply plug in those points – 3 is x and 8 is y.
- 01:07
We get 8 equals m times 3 minus 1
- 01:12
Or, by adding 1 to each side, we have 9 equals 3m.
- 01:16
Our slope is 3… so our answer is C.
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